JP2016065505A - Engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly prevent the overspeed of a turbocharger by decreasing a fuel injection amount by suppressing a rise of a turbo rotation number by boost pressure F/B control.SOLUTION: An engine control device has: a turbocharger 5 having a compressor 5a, a turbine 5b and a movable flap 5c; and an ECU 60 which sets target boost pressure on the basis of an operation state of an engine E, and controls a VGT opening (flap opening) of the turbocharger 5 so that actual boost pressure is set at the target boost pressure. When a turbo rotation number is not smaller than a first prescribed value, the ECU 60 performs control for decreasing a fuel injection amount in order to decrease a rotation number of the turbocharger 5, and performs control for limiting a change of the VGT opening to a closing side by boost pressure F/B control.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an engine control device, and more particularly, to an engine control device that prevents over-rotation of a turbocharger.

  Conventionally, an engine with a turbocharger that supercharges intake air by driving a compressor by rotating a turbine with exhaust gas is known. In such a turbocharger, over-rotation (in other words, supercharging and over-exhaust pressure) may occur depending on operating conditions and the like, and if the over-rotation continues, the turbocharger may be damaged. For this reason, various techniques for preventing excessive rotation of the turbocharger have been proposed. For example, Patent Document 1 proposes a technique for reducing the fuel injection amount when the turbocharger is over-rotated. Specifically, Patent Document 1 proposes a technique for reducing the fuel injection amount when the turbine speed is equal to or higher than the set value even when the boost pressure is less than the set value.

JP-A-5-280385

  By the way, conventionally, a variable geometry turbocharger (VGT) in which a plurality of movable flaps (in other words, movable vanes or nozzle vanes) are arranged around the turbine has been used as a turbocharger. The feedback control for changing the flap opening degree of the turbocharger so as to realize the target boost pressure according to the operating state of the engine (a control referred to as a boost pressure feedback control is described below. F / B control "). When such supercharging pressure F / B control is executed when the fuel injection amount is reduced to prevent over-rotation of the turbocharger as described above, the following problems occur.

  If the fuel injection amount is reduced so as to reduce the turbo rotation speed when the turbocharger is over-rotating, the actual supercharging pressure is reduced. If the supercharging pressure F / B control is executed at this time, the reduced actual supercharging pressure (specifically, the actual supercharging pressure decreased below the target supercharging pressure) is increased, that is, the target overpressure is increased. Control is performed to change the flap opening degree of the turbocharger to the closed side so that the actual supercharging pressure deviating from the supply pressure is increased toward the target supercharging pressure. As a result, the turbo rotation speed increases. For this reason, the supercharging pressure F / B control has an effect that is contrary to the decrease in the fuel injection amount that attempts to reduce the turbo rotational speed in order to prevent the turbocharger from over-rotating. Therefore, when the supercharging pressure F / B control is executed when the fuel injection amount is reduced to prevent the turbocharger from over-rotating, it is possible to appropriately prevent the turbo-supercharger from over-rotating. It becomes impossible.

  The present invention has been made to solve the above-described problems of the prior art, and suppresses an increase in turbo rotation speed due to supercharging pressure F / B control, and reduces the fuel injection amount to reduce the turbocharger. An object of the present invention is to provide an engine control device that can appropriately prevent over-rotation of the engine.

In order to achieve the above-mentioned object, the present invention is an engine control device comprising a turbine provided in an exhaust passage and a compressor provided in an intake passage, and rotating the turbine by exhaust gas to thereby compress the compressor. A turbocharger that supercharges intake air by driving the turbocharger, further comprising a movable flap that can adjust the supercharging pressure, and setting a target supercharging pressure based on the operating state of the engine The flap control means for controlling the flap opening, which is the flap opening of the turbocharger, and the rotational speed of the turbocharger are set so that the actual supercharging pressure is set to the target supercharging pressure. 1 When the fuel injection amount to be supplied to the engine is reduced, control is performed to limit the change of the flap opening to the closing side by the flap control means, and the turbocharger speed is controlled. And having a turbo speed reduction control means for reducing the number, the.
In the present invention configured as described above, when the turbocharger is over-rotated, the control is performed so as to reduce the fuel injection amount and the supercharging pressure that is executed so as to achieve the target supercharging pressure. Since the control (specifically, the supercharging pressure F / B control) is performed to limit the change of the flap opening to the closing side, the increase in turbo rotation speed due to this supercharging pressure control is suppressed, and the fuel The excessive rotation of the turbocharger can be appropriately prevented by reducing the injection amount.

In the present invention, preferably, the turbo rotational speed reduction control means performs control to fix the flap opening degree to the opening degree set when the rotational speed of the turbocharger becomes equal to or higher than the first predetermined value. The change to the closing side of the flap opening degree by the flap control means is limited.
In the present invention configured as described above, since the flap opening degree is controlled to be fixed to the opening degree that is set when the turbocharger is over-rotated, the change of the flap opening degree to the closing side is performed. Can be reliably limited, and an increase in the turbo rotational speed can be effectively suppressed.

In the present invention, preferably, the turbo rotational speed reduction control means performs control to limit the change of the flap opening degree to the closing side by the flap control means after reducing the fuel injection amount, and after this control, the flap opening is performed. Set the degree to full open.
In the present invention configured as described above, after performing the control for reducing the fuel injection amount and the control for limiting the change of the flap opening to the closing side, the flap opening is set to full open, so the fuel injection Even if the turbocharger overspeed is not eliminated by reducing the amount, the turbocharger can be prevented from being overrotated by setting the flap opening degree to fully open.

In the present invention, preferably, when the rotational speed of the turbocharger is reduced to less than the second predetermined value by the control by the turbo rotational speed reduction control means, the reduction of the fuel injection amount is stopped and the fuel injection is resumed. There is further provided a return control means for performing control and restarting the control of the flap opening degree based on the target boost pressure by the flap control means after this control.
In the present invention configured as described above, when the turbocharger overspeed is eliminated by the control by the turbo rotation speed reduction control means, the control for returning the fuel injection is performed, and after this control, the target boost pressure is controlled. Since the supercharging pressure control for realizing the above is restarted, that is, these controls are returned in order without returning at the same time, torque fluctuations and sound changes accompanying the return can be appropriately suppressed.

  According to the engine control apparatus of the present invention, it is possible to suppress an increase in the turbo rotation speed due to the supercharging pressure F / B control, and to appropriately prevent an overspeed of the turbocharger by reducing the fuel injection amount. .

1 is a schematic configuration diagram of an engine system to which an engine control device according to an embodiment of the present invention is applied. It is the longitudinal cross-sectional view which expanded the turbine chamber of the turbocharger by embodiment of this invention. It is explanatory drawing of the high voltage | pressure EGR area | region, low voltage | pressure EGR area | region, and non-EGR area | region by embodiment of this invention. It is a flowchart which shows the basic control by embodiment of this invention. It is a time chart in the turbo excessive rotation prevention control by embodiment of this invention. It is a flowchart which shows the turbo excessive rotation prevention control flow by embodiment of this invention.

  Hereinafter, an engine control apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.

<System configuration>
First, an engine system to which an engine control apparatus according to an embodiment of the present invention is applied will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of an engine system to which an engine control apparatus according to an embodiment of the present invention is applied.

  As shown in FIG. 1, the engine system 200 mainly includes an engine E as a diesel engine, an intake system IN that supplies intake air to the engine E, a fuel supply system FS that supplies fuel to the engine E, It has an exhaust system EX that exhausts exhaust gas from the engine E, sensors 99 to 122 that detect various states relating to the engine system 200, and an ECU (Electronic Control Unit) 60 that controls the engine system 200.

First, the intake system IN has an intake passage 1 through which intake air passes, and an air cleaner 3 that purifies air introduced from the outside in order from the upstream side, and intake air that passes through the intake passage 1. The compressor 5a of the turbocharger 5 that compresses and raises the intake pressure, the intake shutter valve 7 that adjusts the flow rate of the intake air that passes through, and the water-cooled intercooler that cools the intake air using the coolant that has passed through 8 and an electric water pump 9 for controlling the flow rate of the cooling water flowing through the intercooler 8, and the intercooler 8 and the electric water pump 9 are connected to each other, and the cooling water is a passage for circulating the cooling water therebetween. A passage 10 and a surge tank 12 that temporarily stores intake air supplied to the engine E are provided.
In the intake system IN, an air flow sensor 101 for detecting the intake air amount and an intake air temperature sensor 102 for detecting the intake air temperature are provided on the intake passage 1 immediately downstream of the air cleaner 3. 5 is provided with a turbo rotational speed sensor 103 for detecting the rotational speed (turbo rotational speed) of the compressor 5a, and the intake shutter valve 7 is provided with an intake shutter for detecting the opening degree of the intake shutter valve 7. A valve position sensor 105 is provided, and an intake air temperature sensor 106 for detecting the intake air temperature and an intake air pressure sensor 107 for detecting the intake air pressure are provided on the intake passage 1 immediately downstream of the intercooler 8. Is provided with an intake manifold temperature sensor 108. These various sensors 101 to 108 provided in the intake system IN output detection signals S101 to S108 corresponding to the detected parameters to the ECU 60, respectively.

Next, the engine E includes an intake valve 15 for introducing the intake air supplied from the intake passage 1 (specifically, an intake manifold) into the combustion chamber 17, a fuel injection valve 20 for injecting fuel toward the combustion chamber 17, A glow plug 21 as an auxiliary heat source for ensuring ignition at the time of starting, a piston 23 reciprocating by combustion of the air-fuel mixture in the combustion chamber 17, and a crankshaft 25 rotated by reciprocating motion of the piston 23 And an exhaust valve 27 for discharging exhaust gas generated by the combustion of the air-fuel mixture in the combustion chamber 17 to the exhaust passage 41. Further, the engine E is provided with an alternator 26 that generates electric power using the output of the engine E.
The engine E also includes a coolant temperature sensor 109 that detects the temperature of coolant that cools the engine E, the crank angle sensor 110 that detects the crank angle of the crankshaft 25, and the oil pressure and / or oil temperature. An oil pressure / oil temperature sensor 111 for detecting the oil level and an optical oil level sensor 112 for detecting the oil level are provided. These various sensors 109 to 112 provided in the engine E output detection signals S109 to S112 corresponding to the detected parameters to the ECU 60, respectively.

Next, the fuel supply system FS includes a fuel tank 30 for storing fuel, and a fuel supply passage 38 for supplying fuel from the fuel tank 30 to the fuel injection valve 20. In the fuel supply passage 38, a low-pressure fuel pump 31, a high-pressure fuel pump 33, and a common rail 35 are provided in order from the upstream side. The low pressure fuel pump 31 is provided with a fuel warmer 32, the high pressure fuel pump 33 is provided with a fuel pressure regulator 34, and the common rail 35 is provided with a common rail pressure reducing valve 36.
In the fuel supply system FS, the high-pressure fuel pump 33 is provided with a fuel temperature sensor 114 that detects the fuel temperature, and the common rail 35 is provided with a fuel pressure sensor 115 that detects the fuel pressure. These various sensors 114 and 115 provided in the fuel supply system FS output detection signals S114 and S115 corresponding to the detected parameters to the ECU 60, respectively.

Next, the exhaust system EX has an exhaust passage 41 through which the exhaust gas passes. The exhaust passage 41 is rotated by the exhaust gas passing through the exhaust passage 41 in order from the upstream side. A turbine 5b of the turbocharger 5 that drives the compressor 5a, a diesel oxidation catalyst (DOC) 45 and a diesel particulate filter (DPF) 46 having an exhaust gas purification function, and a passage And an exhaust shutter valve 49 for adjusting the exhaust flow rate. The DOC 45 is a catalyst that oxidizes hydrocarbon (HC), carbon monoxide (CO), and the like using oxygen in the exhaust gas to change it into water and carbon dioxide, and the DPF 46 is a particulate substance ( It is a filter that collects PM (Particulate Matter).
In the exhaust system EX, an exhaust pressure sensor 116 for detecting the exhaust pressure and an exhaust temperature sensor 117 for detecting the exhaust temperature are provided on the exhaust passage 41 on the upstream side of the turbine 5b of the turbocharger 5. Exhaust temperature sensors 118 and 119 for detecting the exhaust temperature are provided immediately upstream of the DOC 45 and between the DOC 45 and the DPF 46, respectively. The DPF 46 has the exhaust pressure of the upstream side and the downstream side of the DPF 46. A DPF differential pressure sensor 120 for detecting the difference is provided, and a linear O ₂ sensor 121 for detecting the oxygen concentration and an exhaust temperature sensor 122 for detecting the exhaust temperature are provided on the exhaust passage 41 immediately downstream of the DPF 46. ing. These various sensors 116 to 122 provided in the exhaust system EX output detection signals S116 to S122 corresponding to the detected parameters to the ECU 60, respectively.

  Further, in the present embodiment, the turbocharger 5 is configured in a small size so as to be able to perform supercharging efficiently even during low-speed rotation with low exhaust energy, and a plurality of movable parts so as to surround the entire circumference of the turbine 5b. Type flaps 5c are provided, and these flaps 5c are configured as variable geometry turbochargers (VGTs) that change the flow cross-sectional area (nozzle cross-sectional area) of the exhaust gas to the turbine 5b. . For example, the flap 5c is rotated by an actuator with the magnitude of the negative pressure acting on the diaphragm adjusted by an electromagnetic valve. Further, a VGT opening sensor 104 is provided for detecting the opening of the flap 5c (which is the flap opening, hereinafter referred to as “VGT opening” as appropriate) depending on the position of the actuator. The VGT opening sensor 104 outputs a detection signal S104 corresponding to the detected VGT opening to the ECU 60.

Here, the flap 5c of the turbocharger 5 according to the embodiment of the present invention will be specifically described with reference to FIG. FIG. 2 schematically shows a configuration of a longitudinal section in which the turbine chamber of the turbocharger 5 is enlarged.
As shown in FIG. 2, a plurality of movable flaps 5c, 5c,... Are arranged in a turbine chamber 153a formed in the turbine casing 153 so as to surround the periphery of the turbine 5b arranged at the substantially central portion thereof. Each flap 5c is rotatably supported by a support shaft 131a passing through one side wall of the turbine chamber 153a. When the respective flaps 5c are rotated clockwise in FIG. 2 around the supporting shaft 5d and inclined so as to be close to each other, the nozzles 155, 155,... Formed between the respective flaps 5c are opened. The degree (nozzle cross-sectional area) is narrowed down, and high supercharging efficiency can be obtained even when the exhaust gas flow rate is small. On the other hand, if each flap 5c is rotated to the opposite side and inclined so as to be separated from each other, the cross-sectional area of the nozzle increases. Efficiency can be increased.
The ring member 157 is drivingly connected to the rod 163 of the actuator via the link mechanism 158, and the flaps 5c are rotated via the ring member 157 by the operation of the actuator. That is, the link mechanism 158 includes a connection pin 158a whose one end is rotatably connected to the ring member 157, and a connection plate member 158b whose one end is rotatably connected to the other end of the connection pin 158a. The columnar member 158c is coupled to the other end of the coupling plate member 158b, and one end is coupled to the columnar member 158c penetrating the outer wall of the turbine casing 153 and the protruding end of the columnar member 158c projecting out of the turbine casing 153. The other end of the connecting plate member 158d is rotatably connected to the rod 163 of the actuator by a connecting pin (not shown).

  Returning to FIG. 1, the engine system 200 according to the present embodiment further includes a high-pressure EGR device 43 and a low-pressure EGR device 48. The high-pressure EGR device 43 connects the exhaust passage 41 upstream of the turbine 5b of the turbocharger 5 and the intake passage 1 downstream of the compressor 5b of the turbocharger 5 (specifically, downstream of the intercooler 8). And a high pressure EGR valve 43b that adjusts the flow rate of exhaust gas that passes through the high pressure EGR passage 43a. The low pressure EGR device 48 includes an exhaust passage 41 on the downstream side of the turbine 5b of the turbocharger 5 (specifically, on the downstream side of the DPF 46 and the upstream side of the exhaust shutter valve 49) and the upstream side of the compressor 5b of the turbocharger 5. A low pressure EGR passage 48a that connects the intake passage 1 of the engine, a low pressure EGR cooler 48b that cools the exhaust gas that passes through the low pressure EGR passage 48a, and a low pressure EGR valve 48c that adjusts the flow rate of the exhaust gas that passes through the low pressure EGR passage 48a. And a low pressure EGR filter 48d.

  The amount of exhaust gas recirculated to the intake system IN by the high pressure EGR device 43 (hereinafter referred to as “high pressure EGR gas amount”) is the exhaust pressure upstream of the turbine 5 b of the turbocharger 5 and the opening of the intake shutter valve 7. It is generally determined by the intake pressure produced by the degree and the opening degree of the high pressure EGR valve 43b. Further, the amount of exhaust gas recirculated to the intake system IN by the low pressure EGR device 48 (hereinafter referred to as “low pressure EGR gas amount”) is the intake pressure on the upstream side of the compressor 5 a of the turbocharger 5 and the exhaust shutter valve 49. Is roughly determined by the exhaust pressure produced by the opening of the valve and the opening of the low pressure EGR valve 48c.

Here, referring to FIG. 3, in the embodiment of the present invention, the operating region of engine E in which high pressure EGR device 43 is operated (hereinafter referred to as “high pressure EGR region”) and low pressure EGR device 48 are operated. The operation region of the engine E (hereinafter referred to as “low pressure EGR region”) will be described. FIG. 3 shows the engine speed on the horizontal axis and the fuel injection amount (corresponding to the engine load) on the vertical axis, and schematically shows the high pressure EGR region and the low pressure EGR region.
As shown in FIG. 3, the operating region R1 (corresponding to the first operating region) of the engine E defined on the low load / low rotational speed side is a high pressure EGR region where the high pressure EGR device 43 is operated. An operation region R2 (corresponding to the second operation region) of the engine E defined on the high load / high rotation speed side from the high pressure EGR region R1 is a low pressure EGR region in which the low pressure EGR device 48 is operated. More specifically, not only the low pressure EGR device 48 but also the high pressure EGR device 43 is operated in a part of the low pressure EGR region R2 (region near the boundary with the high pressure EGR region R1), that is, the high pressure EGR device 43. And it becomes a combined use area of the low pressure EGR device 48. In addition, the operation region R3 of the engine E, which is defined on the higher load / high rotation speed side than the low pressure EGR region R2, is a region where neither the high pressure EGR device 43 nor the low pressure EGR device 48 is operated (hereinafter referred to as “non-EGR” as appropriate). Area).).

  Returning to FIG. 1, the ECU 60 according to the present embodiment, in addition to the detection signals S101 to S122 of the various sensors 101 to 122 described above, an outside air temperature sensor 98 that detects the outside air temperature, an atmospheric pressure sensor 99 that detects the atmospheric pressure, And the control with respect to the component in the engine system 200 is performed based on detection signal S98-S100 which each of the accelerator opening degree sensor 100 which detects the opening degree (accelerator opening degree) of the accelerator pedal 95 outputs. Specifically, the ECU 60 sends a control signal S130 to an actuator (not shown) that drives the flap 5c in order to control the opening (VGT opening) of the flap 5c in the turbine 5b of the turbocharger 5. Output. Further, the ECU 60 outputs a control signal S131 to an actuator (not shown) that drives the intake shutter valve 7 in order to control the opening degree of the intake shutter valve 7. Further, the ECU 60 outputs a control signal S132 to the electric water pump 9 in order to control the flow rate of the cooling water supplied to the intercooler 8. Further, the ECU 60 outputs a control signal S133 to the fuel injection valve 20 in order to control the fuel injection amount of the engine E and the like. Further, the ECU 60 outputs control signals S134, S135, S136, and S137 to control the alternator 26, the fuel warmer 32, the fuel pressure regulator 34, and the common rail pressure reducing valve 36, respectively. In addition, the ECU 60 outputs a control signal S138 to an actuator (not shown) that drives the high pressure EGR valve 43b in order to control the opening degree of the high pressure EGR valve 43b. Further, the ECU 60 outputs a control signal S139 to an actuator (not shown) that drives the low pressure EGR valve 48c in order to control the opening degree of the low pressure EGR valve 48c. Further, the ECU 60 outputs a control signal S140 to an actuator (not shown) that drives the exhaust shutter valve 49 in order to control the opening degree of the exhaust shutter valve 49.

<Basic control>
Next, basic control implemented in the engine system 200 according to the embodiment of the present invention will be described with reference to FIG. FIG. 4 is a flowchart showing basic control according to the embodiment of the present invention. In this flow, control for realizing the target oxygen concentration and the target intake air temperature according to the required injection amount and the like is performed. This flow is repeatedly executed by the ECU 60 at a predetermined cycle.

First, in step S11, the ECU 60 acquires at least one of the detection signals S98 to S122 output from the various sensors 98 to 122 described above.
Next, in step S12, the ECU 60 sets a target torque to be output from the engine E based on the accelerator opening (corresponding to the detection signal S100) detected by the accelerator opening sensor 100.
Next, in step S13, the ECU 60 sets a required injection amount to be injected from the fuel injection valve 20 based on the target torque set in step S12 and the engine speed.
Next, in step S14, the ECU 60 determines the fuel injection pattern, the fuel pressure, the target oxygen concentration, the target intake air temperature, and the EGR control mode (based on the required injection amount set in step S13 and the engine speed). A mode in which both or one of the high pressure EGR device 43 and the low pressure EGR device 48 is operated, or a mode in which neither the high pressure EGR device 43 nor the low pressure EGR device 48 is operated) is set.
Next, in step S15, the ECU 60 sets state quantities for realizing the target oxygen concentration and target intake air temperature set in step S14. For example, this state quantity includes the amount of exhaust gas recirculated to the intake system IN by the high pressure EGR device 43 (high pressure EGR gas amount) and the amount of exhaust gas recirculated to the intake system IN by the low pressure EGR device 48 (low pressure EGR gas amount). And a supercharging pressure by the turbocharger 5 is included.
Next, in step S16, the ECU 60 controls each actuator that drives each component of the engine system 200 based on the state quantity set in step S15. In this case, the ECU 60 sets a limit value or a limit range according to the state quantity, sets the control amount of each actuator such that the state value complies with the limit value or the limit range, and executes control.

<Turbo overspeed prevention control>
Below, the control (turbo overspeed prevention control) for preventing the overspeed of the turbocharger 5 according to the embodiment of the present invention will be described.

First, an outline of control performed by the ECU 60 in the embodiment of the present invention will be described. In the present embodiment, the ECU 60 sets the target boost pressure based on the operating state of the engine E (specifically, the fuel injection amount and the engine speed), and the actual boost pressure is set to this target boost pressure. In this manner, the opening degree (VGT opening degree) of the flap 5c of the turbocharger 5 is controlled. That is, the ECU 60 uses the supercharging pressure F / B control to change the VGT opening degree so that the target supercharging pressure is realized while comparing the actual supercharging pressure with the target supercharging pressure. Typically, when the actual boost pressure is lower than the target boost pressure, the ECU 60 performs control to change the VGT opening to the closed side, and the actual boost pressure exceeds the target boost pressure. If it is, control is performed to change the VGT opening to the open side.
In the present embodiment, the ECU 60 performs the combustion chamber of the engine E as the turbo overspeed prevention control for preventing the turbocharger 5 from over-rotating when the turbo-supercharger 5 over-rotates. The fuel injection amount supplied to the engine 17 is controlled to be reduced (hereinafter referred to as “injection amount reduction control” as appropriate), and the change of the VGT opening to the closing side by the supercharging pressure F / B control is limited. Control. In this case, the ECU 60 stops execution of the supercharging pressure F / B control, thereby limiting the change of the VGT opening to the closing side due to the supercharging pressure F / B control.

  Thus, the reason for stopping the execution of the supercharging pressure F / B control in the present embodiment is as follows. When the fuel injection amount is reduced by the injection amount reduction control to reduce the turbo rotation speed when the turbocharger 5 is over-rotating, the actual supercharging pressure decreases (especially in the region where the engine rotation speed is large, the actual supercharging pressure). Decrease is significant). If the supercharging pressure F / B control is executed at this time, the reduced actual supercharging pressure (specifically, the actual supercharging pressure decreased below the target supercharging pressure) is increased, that is, the target overpressure is increased. Control is performed to change the VGT opening in the turbocharger 5 to the closed side so that the actual supercharging pressure deviating from the supply pressure is increased toward the target supercharging pressure. As a result, the turbo rotation speed increases. For this reason, the supercharging pressure F / B control causes an operation contrary to the injection amount reduction control that attempts to reduce the turbo rotation speed in order to prevent the turbocharger 5 from over-rotating. That is, the supercharging pressure F / B control is a control contrary to the injection amount reduction control. Therefore, in the present embodiment, when the turbocharger 5 is excessively rotated and the injection amount reduction control is executed, the execution of the supercharging pressure F / B control is stopped.

  Here, as described above, when the fuel injection amount is reduced when the turbocharger 5 is excessively rotated, the exhaust energy (exhaust temperature) is decreased, whereby the turbo rotational speed can be decreased. It is possible to prevent over-rotation. Even when the VGT opening degree in the turbocharger 5 is controlled to the open side, the turbo rotational speed can be reduced. However, in the turbocharger 5 configured to be small, the VGT opening degree is controlled to the open side. However, there is a case in which over-rotation of the turbocharger 5 cannot be properly prevented, and the change in the turbo speed with respect to the control of the VGT opening tends to be delayed (that is, the response of the turbo speed to the control of the VGT opening). Bad nature). On the other hand, when the fuel injection amount is reduced, the turbo rotational speed can be reduced relatively quickly. In addition, the normal fuel injection can be resumed (restarted) after the fuel injection amount has been reduced as compared with the control of the VGT opening degree. Therefore, in this embodiment, in order to prevent the turbocharger 5 from over-rotating, a method of reducing the fuel injection amount by the injection amount reduction control is adopted.

  Note that, when the turbocharger 5 is excessively rotated, the VGT opening is basically set to the open side. Specifically, the VGT opening may be set to an opening on the opening side that still has a margin until fully open, or the VGT opening may be set to fully open. If the VGT opening is not set to fully open, it is possible to perform control to set the VGT opening to fully open in order to prevent over-rotation of the turbocharger 5, but for the reasons described above, In the present embodiment, the ECU 60 stops the supercharging pressure F / B control without immediately performing the control to set the VGT opening fully open, and restricts the change of the VGT opening to the closing side, An injection amount reduction control for reducing the fuel injection amount is performed. In the present embodiment, the ECU 60 performs the protection logic when the overspeed of the turbocharger 5 is not eliminated even if the injection amount reduction control is performed in such a state that the supercharging pressure F / B control is stopped. Then, control for setting the VGT opening to full open is performed.

  As described above, the ECU 60 functions as the “flap control means” and the “turbo rotational speed reduction control means” in the present invention. Although details will be described later, the ECU 60 also functions as “return control means” in the present invention.

  Next, a time chart in the turbo overspeed prevention control according to the embodiment of the present invention will be described with reference to FIG. FIG. 5 shows an example of a time chart when the turbo overspeed prevention control according to the embodiment of the present invention is executed.

  In FIG. 5, in order to compare the result by this embodiment which performed injection amount reduction | decrease control when the turbo turbocharger 5 over-rotated, and such this embodiment, the turbocharger 5 of FIG. The result by the comparative example (henceforth a "1st comparative example") which did not perform injection amount reduction | decrease control when over-rotation occurred is shown. Further, in the control according to the present embodiment shown in FIG. 5, when the turbocharger 5 is over-rotated, the execution of the supercharging pressure F / B control is stopped in addition to the injection amount reduction control. To do. In FIG. 5, in order to compare with this embodiment, when the turbocharger 5 is over-rotated, the injection amount reduction control is executed, but the supercharging pressure F / B control is executed. A result of a comparative example (hereinafter referred to as “second comparative example”) in which the supercharging pressure F / B control is continuously executed without stopping is also shown.

  FIG. 5 will be specifically described. FIG. 5 shows time in the horizontal direction, and shows the turbo rotation speed, fuel injection amount, VGT opening degree, and supercharging pressure in order from the top. Specifically, the graph G11 shows the time change of the turbo rotation speed according to the present embodiment, and the graph G12 shows the time change of the turbo rotation speed according to the first comparative example. Further, the graph G21 shows the time change of the fuel injection amount according to the present embodiment, and the graph G22 shows the time change of the fuel injection amount by the first comparative example. Further, the graph G31 shows the time change of the VGT opening according to the present embodiment, and the graph G32 shows the time change of the VGT opening according to the second comparative example. The graph G41 shows the time change of the actual supercharging pressure according to this embodiment, the graph G42 shows the time change of the actual supercharging pressure according to the second comparative example, and the graph G43 shows the operating state of the engine E (engine The time change of the target supercharging pressure set based on the rotational speed, the fuel injection amount, etc.) is shown.

  At time t1, it is assumed that the opening degree of the accelerator pedal 95 (accelerator opening degree) has changed in the stepping direction due to an acceleration request from the driver (not shown in FIG. 5). For this reason, the fuel injection amount is increased from time t1 (see graphs G21 and G22), and the target boost pressure is increased by the boost pressure F / B control (see graph G43). The opening degree (see graphs G31 and G32) is controlled, and the actual supercharging pressure (see graphs G41 and G42) and the turbo speed (see graphs G11 and G12) increase. Thereafter, at time t2, the turbo rotation speed becomes equal to or greater than the predetermined value Th1 (see graphs G11 and G12), that is, the turbocharger 5 is overrotated.

  According to the first comparative example, the fuel injection amount applied at time t2 is substantially maintained even after time t2 (see graph G22). For this reason, the turbo rotational speed continues to increase after time t2 (see graph G12), that is, the state where the turbo rotational speed is equal to or greater than the predetermined value Th1 continues, and the overspeed of the turbocharger 5 is not eliminated. On the other hand, according to the present embodiment, the injection amount reduction control for reducing the fuel injection amount is executed at time t2 (see graph G21). Therefore, the turbo rotation speed decreases after time t2 (see graph G11). In this case, the turbo rotation speed is reduced to less than the predetermined value Th1, and the overspeed of the turbocharger 5 is eliminated.

On the other hand, according to the second comparative example, the injection amount reduction control is executed, but the actual supercharging pressure (see graph G42) decreased by the reduction of the fuel injection amount by this injection amount reduction control is set to the target supercharging pressure (graph The VGT opening degree is controlled to the close side by the supercharging pressure F / B control so as to increase to (see G43) (see graph G32). In such a case, the turbo rotation speed increases (not shown in FIG. 5). In contrast, according to the present embodiment, when the injection amount reduction control is executed, the supercharging pressure F / B control is stopped, so that the VGT opening is fixed to a substantially constant opening (see graph G31). ), That is, the change of the VGT opening to the closing side is suppressed. In this case, the actual boost pressure (see graph G41) deviates from the target boost pressure (see graph G43). According to this embodiment, since the increase in the turbo rotation speed due to the supercharging pressure F / B control is suppressed, the turbo rotation speed is effectively reduced by the injection amount reduction control described above ( (See graph G11).
Note that at time t2 when the turbo rotation speed reaches the predetermined value Th1, both the present embodiment and the second comparative example assume that the VGT opening is almost fully open (see graphs G31 and G32). .

Next, the overall flow of the turbo overspeed prevention control according to the embodiment of the present invention will be specifically described with reference to FIG. FIG. 6 is a flowchart showing a turbo overspeed prevention control flow according to the embodiment of the present invention. This turbo overspeed prevention control flow is repeatedly executed by the ECU 60 at a predetermined cycle.
This turbo overspeed prevention control flow is based on the premise that supercharging pressure F / B control for changing the VGT opening degree is executed so that the target supercharging pressure is realized at the start of execution of the flow. Yes.

  Here, the outline of the turbo overspeed prevention control flow will be briefly described. In the turbo overspeed prevention control flow, the ECU 60 first executes the injection amount reduction control for reducing the fuel injection amount when the turbo rotation speed becomes equal to or higher than the first predetermined value, and the supercharging pressure F / B control. Stop running. The ECU 60 continues the execution of the injection amount reduction control and the stop of the supercharging pressure F / B control until the turbo rotation speed becomes less than the second predetermined value. Then, when the turbo rotation speed becomes less than the second predetermined value, the ECU 60 performs control (hereinafter referred to as “injection return control”) for stopping the injection amount reduction control and returning the normal fuel injection. Thereafter, the supercharging pressure F / B control is resumed.

  The turbo overspeed prevention control flow of FIG. 6 will be specifically described. First, in step S21, the ECU 60 determines whether or not the rotational speed (turbo rotational speed) of the compressor 5a of the turbocharger 5 detected by the turbo rotational speed sensor 103 is equal to or greater than a first predetermined value. This first predetermined value is a threshold value for determining whether or not the turbocharger 5 is over-rotated, and the rotation speed (for example, the compressor 5a) corresponding to the over-rotation of the compressor 5a of the turbocharger 5 is determined. Is set based on the number of revolutions at which damage or the like may occur. For example, the first predetermined value is set to 255000 rpm.

  As a result of the determination in step S21, if it is not determined that the turbo rotation speed is equal to or greater than the first predetermined value (step S21: No), that is, if the turbo rotation speed is less than the first predetermined value, the process ends. In this case, since the turbocharger 5 is not overrotated, the ECU 60 does not execute the turbo overspeed prevention control according to the present embodiment.

  On the other hand, when it is determined that the turbo rotational speed is equal to or higher than the first predetermined value (step S21: Yes), the process proceeds to step S22, and the ECU 60 controls the fuel injection valve 20 of the engine E to In order to reduce the rotational speed, the injection amount reduction control for reducing the fuel injection amount is executed. In one example, the ECU 60 reduces the fuel injection amount by a predetermined amount. In another example, the ECU 60 reduces the fuel injection amount according to the degree to which the turbo rotation speed exceeds the first predetermined value.

Next, the ECU 60 proceeds to step S23, and the ECU 60 controls the engine pressure to suppress the increase in the turbo rotation speed due to the supercharging pressure F / B control, that is, to suppress the contradiction between the supercharging pressure F / B control and the injection amount reduction control. Supply pressure F / B control is stopped. In this case, the ECU 60 stops the execution of the supercharging pressure F / B control and restricts the change of the VGT opening to the closing side due to the supercharging pressure F / B control.
In one example, the ECU 60 prohibits the change of the VGT opening to the closing side by allowing the supercharging pressure F / B control to be stopped, and allows the change of the VGT opening to the opening side. And the VGT opening degree is controlled. In this example, the ECU 60 does not change the VGT opening to the closing side, but appropriately changes the VGT opening to the opening side as necessary.
In another example, the ECU 60 stops the execution of the supercharging pressure F / B control, and performs control to fix the VGT opening to the opening that was set when the turbocharger 5 overrotated. And limit the change of the VGT opening to the closing side. In this example, the ECU 60 fixes the VGT opening and does not change the VGT opening.

  Next, the process proceeds to step S24, where the ECU 60 determines whether or not the rotational speed (turbo rotational speed) of the compressor 5a of the turbocharger 5 detected by the turbo rotational speed sensor 103 is less than a second predetermined value. This second predetermined value is a threshold value for determining whether or not the overspeed of the turbocharger 5 has been eliminated. Similar to the first predetermined value, the second predetermined value corresponds to the overspeed of the compressor 5a of the turbocharger 5. The rotation speed is set based on the corresponding rotation speed (for example, the rotation speed at which the compressor 5a can be damaged). For example, the second predetermined value is set to 250,000 revolutions / minute, which is slightly lower than the first predetermined value. The second predetermined value is not limited to being set to a value different from the first predetermined value, and the second predetermined value may be set to the same value as the first predetermined value.

  As a result of the determination in step S24, if it is not determined that the turbo rotation speed is less than the second predetermined value (step S24: No), that is, if the turbo rotation speed is greater than or equal to the second predetermined value, the process proceeds to step S22. Returning, the ECU 60 executes the injection amount reduction control again to further reduce the fuel injection amount. For example, the ECU 60 further reduces the fuel injection amount after the previous reduction by a predetermined amount. And ECU60 continues the state which stopped the supercharging pressure F / B control in step S23.

  The ECU 60 repeats the processes of steps S22 to S24 as described above, and gradually reduces the fuel injection amount while comparing the turbo rotation speed with the second predetermined value in a state where the supercharging pressure F / B control is stopped. Go. As a result, if the turbo rotation speed does not become less than the second predetermined value even when the fuel injection amount is reduced to a predetermined amount (for example, 0), that is, if the overspeed of the turbocharger 5 is not eliminated, the ECU 60 Performs control to set the VGT opening to fully open (assuming that the VGT opening is not fully open when the injection amount reduction control is executed).

  On the other hand, when it is determined that the turbo rotation speed is less than the second predetermined value (step S24: Yes), the process proceeds to step S25. In this case, since the turbocharger 5 has not been over-rotated, in step S25, the ECU 60 stops the injection amount reduction control and injects an amount of fuel corresponding to the accelerator opening, the engine speed, and the like. In order to resume normal fuel injection, injection return control is executed. In this case, the ECU 60 returns the fuel injection after a lapse of time such that the occupant does not feel a change in torque or sound.

  Next, in step S26, the ECU 60 resumes the supercharging pressure F / B control for setting the actual supercharging pressure to the target supercharging pressure corresponding to the operating state of the engine E. That is, the ECU 60 sets the target boost pressure in accordance with the engine speed, the fuel injection amount, etc., and compares the actual boost pressure with the target boost pressure so that the target boost pressure is realized. The supercharging pressure F / B control that changes the degree is restarted.

<Effect>
Next, functions and effects of the engine control apparatus according to the embodiment of the present invention will be described.

According to the present embodiment, when the turbocharger 5 is over-rotated, the injection amount reduction control for reducing the fuel injection amount is performed, and the VGT opening degree is closed by the supercharging pressure F / B control. Therefore, it is possible to appropriately prevent the turbocharger 5 from over-rotation by reducing the fuel injection amount by suppressing the increase in the turbo rotation speed due to the supercharging pressure F / B control. .
Specifically, in this embodiment, since the VGT opening is controlled to be fixed at the opening set when the turbocharger 5 is over-rotated, the change of the VGT opening to the closing side is performed. Can be reliably limited, and an increase in the turbo rotational speed can be effectively suppressed.

  In addition, according to the present embodiment, the VGT opening is set to fully open after the injection amount reduction control and the supercharging pressure F / B control are stopped, so that the turbocharger 5 is controlled by the injection amount reduction control. Even if the rotation is not eliminated, the turbocharger 5 can be prevented from over-rotating by setting the VGT opening degree to fully open.

  Further, according to the present embodiment, when the turbo turbocharger 5 is over-resolved by the turbo overspeed prevention control, the injection return control is performed, and the supercharging pressure F / B control is resumed after this control. In other words, the injection return control and the supercharging pressure F / B control are not restarted at the same time, but the injection return control and the supercharging pressure F / B control are restarted in this order. Can be suppressed appropriately.

1 intake passage 5 turbocharger 5a compressor 5b turbine 5c flap 20 fuel injection valve 41 exhaust passage 43 high pressure EGR device 45 DOC
46 DPF
48 Low pressure EGR device 60 ECU
200 engine system E engine

Claims (4)

An engine control device,
A turbocharger comprising a turbine provided in an exhaust passage and a compressor provided in an intake passage, wherein the compressor is driven by rotating the turbine by exhaust gas to supercharge intake air. The turbocharger further comprising a movable flap whose pressure can be adjusted;
The target boost pressure is set based on the engine operating state, and the flap opening degree that is the flap opening degree of the turbocharger is controlled so that the actual boost pressure is set to the target boost pressure. Flap control means;
When the rotational speed of the turbocharger is greater than or equal to a first predetermined value, control is performed to reduce the fuel injection amount supplied to the engine, and the flap control means changes the flap opening to the closed side. Turbo speed reduction control means for performing limiting control and reducing the rotational speed of the turbocharger;
An engine control device comprising:   The turbo rotational speed reduction control means performs control for fixing the flap opening degree to an opening degree that was set when the rotational speed of the turbocharger became equal to or greater than the first predetermined value, and The engine control apparatus according to claim 1, wherein a change in the flap opening degree toward the closing side by the control means is limited.   The turbo rotational speed reduction control means performs control to limit the change of the flap opening degree to the closing side by the flap control means after reducing the fuel injection amount. The engine control device according to claim 1, wherein the engine control device is set to be fully open.   When the rotational speed of the turbocharger is reduced to less than a second predetermined value by the control by the turbo rotational speed reduction control means, a control is performed to stop the decrease in the fuel injection amount and return the fuel injection, The engine control according to any one of claims 1 to 3, further comprising return control means for resuming control of the flap opening degree based on the target boost pressure by the flap control means after the control. apparatus.

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